1. Field of the Invention
This invention relates to an in-mold label applying device and more particularly to one capable of shortening a molding cycle time and improving accuracy of application of a label.
2. Description of the Related
The so-called in-mold labeling is practiced in which, when a blow molded container is manufactured by blow molding, mold halves are closed for blow molding after a label is applied (temporary deposition) to an inner surface of each container, so that the label is integrally attached to the surface of the hollow molded container.
The above-mentioned application of a label to an inner surface of each mold half is automatically carried out by an in-mold label applying device. Heretofore, the in-mold label applying device was actuated using two drive sources, namely, an air cylinder or motor for bringing the label into a space between mold halves which are in an open position, and an air cylinder or motor for transferring the label brought into the space between the mold halves to an inner surface of one of the mold halves.
However, this conventional device had problems such that, since there is a need of a provision of two drive sources corresponding to two axial directions perpendicular to each other, manufacturing costs are increased and the mechanism is complex, thus resulting in failure. Moreover, because the second operation must be performed after making sure that the first operation is finished, a time loss occurs for such sure performance. A further problem was also encountered in that, since the drive mechanism must be mounted on an arm portion for applying a label, the arm portion is increased in weight which makes it difficult for the arm portion to follow a high-speed operation.
As one for improving the above problems, U.S. Pat. No. 4,549,863 discloses an in-mold label applying device in which a label is brought into a space between mold halves which are in an open position and attached to the inner walls of the mold halves by a single drive mechanism. A representative one out of a plurality of in-mold label applying devices described in U.S. Pat. No. 4,549,863 is shown in FIG. 7.
In the prior art in-mold label applying device shown in FIG. 7, when main arm 1' for depositing a label L' comes into the space between an opened metal mold M' a prescribed distance, a case portion 2'contacts the metal mold M' and a stopper 5'. Then, a piston 4', a sub-arm 3'and the main arms 1'are cooperated to apply the label L' attached to the distal ends of the main arms 1'to the inner surface of the metal mold M' in a way as indicated by broken lines of FIG. 7.
With the use of the in-mold label applying device of FIG. 7, however, application accuracy of the label L' is degraded because the orbit of the label L' exhibits a circular arc when the label L' is deposited on the inner surface of the metal mold M'. In addition, it gives rise to another problem in that damage is liable to occur due to rubbing of the label L'. Moreover, there is a further problem in that, when the configuration of a hollow container to be molded is changed, the configurations of the arms 1'and 3'must also be changed taking into account among others, an angle of contact of the label L' with the inner surface of the metal mold M'.